Adapting sheet metal elements for screws



Aug. 851939.. K B E 2,169,057

ADAPTING 5mm METAL ELEMENTS FOR SCREWS 'Fi ledlApril 16, 1938 9 5/0 C /ace @54 MW s MAW atented Aug. 8, 1939 um'rso STATES PATENT OFFICE ADAPTING SHEET METAL ELEMENTS FOB SCREWS Dion 0. Place, Detroit, Mich., assignor to Prestole Devices, Inc., Detroit, Mich, a corporation of Michigan Application April 1c, 1938, Serial No. 202,566

4 Claims.

out rendering the sheet metal structure pervlous metal element at the slit formed therein. Ac-

, cordingly, when the invention of said patent is applied in situations in which the sheet metal element is relied upon to prevent the passage of foreign substances therethrough, said slit bei comes objectionable.

It has been further; found that when heavy pressure is exerted against the top of the cone,

by means of a screw having a strong thread, that,

occasionally, the two edges of the radially extending slit are caused to pass each other thus distorting the shape of the opening in thettop of the protuberance so that the sheet metal does not grip the base of the thread of the screw substantially uniformly around the circumference of the screw, as is most desirable for eilicient self-locking action upon the screw.

The primary purpose of the present invention is to provide a generally conical protuberance having an opening in the top thereof shaped to provide a single thread for a screw, in which the high and low points of the single thread are obtained by offsetting a portion of the protuberance to form an upstanding radial web rather than by slitting the same.

A further object of the invention is to provide sheet metal structures with a self-locking thread formed by bossing the metal adjacent the screw receiving opening therein so that a substantially complete thread is provided by the wall of each opening without slitting the protuberance formed by the bossing, except only to the depth of the thread of the screw for which the sheet metal structure is adapted.

Another object of the invention is to provide an improved method of adapting a sheet metal structure for the reception of a screw including the formation of a protuberance in the metal surrounding the opening for the screw, and the offsetting of. the metal of the protuberance to form an integral web between the high and low points of a thread provided by the wall of the opening.

Still another object of the invention is to containing the screw receiving opening, which protuberance is provided with a radial offset presenting a substantial vertically extending wall or web to the thread of the screw, which wall or web may be perforated by the thread to the extent necessary to permit threaded engagement by the screw, said offset web otherwise thus presenting an imperforate wall.

Still another object of the invention is to provide a sheet metal structure with a protuberance having a screw receiving, opening in the top thereof which possesses great resistance against forces tending to flatten it, and which, when partially flattened, is certain to substantially evenly grip the shank of the screw at the base of the thread engaged therewith throughout substantially the entire circumference of said shank.

Still another object of the invention is to provide an improved method of providing a threaded engagement between a sheet metal structure and a screw consisting of embossing the metal around the screw opening, forming an offset web radiating from the opening in the embossment, and then causing the thread of the screw to itself out its passage through the web provided by said offset, whereby the screw is engaged with said structure with a minimum perforation of the structure.

Still further objects of the invention will appear as the description thereof proceeds with reference to the accompanying drawing in which:

Figure 1 is a side elevational view of a fragment of a sheet metal structure or element adapted for the reception of a screw in accordance with the present invention;

Figure 2 is a plan view of the fragment illus- 'trated in Figure. 1;

Figures 3 and 4 are respectively sectional views taken on the plane indicated by the lines 3-3 and l-l of Figure 2;

Figure 5 is a sectional view showing the sheet metal element or structure secured to a further screw being shown prior to tightening thereof;

Figure 6 is a view corresponding to Figure 5, but showing the screw drawn taut to produce a locking between the screw and the sheet metal structure or element;

Figure '7 is a plan view of a sheet metal nut adapted for the reception of a screw in accordance with the present invention; and

Figure 8 is a sectional view taken on the plane indicated by the line 8-8 in Figure 7.

Like reference characters indicate like parts throughout the several figures.

Numeral l0 designates a fragment of a sheet metal element or structure provided with a generally conical protuberance ii having an opening i2 in the top thereof. The wall iii of the opening (2 is shaped to provide a single helical thread having a pitch corresponding substantially to the pitch of a screw which is to be engaged with the structure or element. An offset web 14 extends radially of the protuberance, said offset web having its maximum height adjacent the opening and diminishing in height toward the base of the protuberance where it disappears in the plane of the metal structure or element, as illustrated. The offset web provides the high point l5 (Figure 4) of the single thread provided by the edge of the opening and the low point I6 of said thread.

The protuberance has a base that is wide compared to the diameter of the opening in the top thereof, the width of the protuberance at its base preferably exceeding twice the diameter of said opening. Said diameter corresponds approximately to the diameter of the screw intended to be threaded into said opening at the base of the thread thereof. The protuberance is also made relatively deep, the preferred arrangement inolving protuberance having its lowest point l6 spaced above the adjacent structure a distance at least equal to the pitch of the screw to be engaged therewith for the purpose hereinafter to be referred to.

Preferably the protuberance H has a base merging into the plane of the structure or element on a smooth curve l'l, that is concave as seen from the top of the element or structure. Adjacent the top of the protuberance the metal is preferably curved inwardly on a smooth curve l8, that is convex as seen from the top of the protuberance so that the wall "5 of the opening I2 is disposed normal, or substantially normal, to the plane of the element or structure l0. Inasmuch as it has been found that a protuberance having the concave-convex form just referred to possesses the greatest strength against pressures applied to the top thereof by the action of the screw, and exerts, when flattened, the most effective gripping pressure against the shank of the screw, protuberances having this form are preferred. However. it should be understood that the scope of the present invention contemplates the utilization of any protuberance designated as generally conical. Also. protuberances shaped so that the wall of the opening extends at an acute angle to a plane normal to the metal element or structure are within the purview of the present invention.

Sheet metal elements or structures may be provided with protuberances such as just described either in a single stamping operation, or in multiplicity of stamping'operations, as may be preferred. Preferably, they are formed in a single stamping and punching operation, the opening being first formed in the sheet metal element or structure and then the metal surrounding said opening brought into the shape already described by pressure between mating dies. When the protuberance has been completed, the opening i2 is preferably circular. While some drawing or stretching of the metal is necessary to form the described protuberance, it has been found that sheet metal will successfully withstand such stretching without rupture. The point of maximum stretching of the metal is at the point of formation of the offset web i4 and, preferably, the protuberance is formed without rupturing the metal at this point. If desired, however, the protuberance may be formed so that the edge of the offset web is ruptured or weakened to facilitate the threading of the screw through the sheet metal structure in the manner presently to be referred to.

The manner in which a sheet metal element or structure, such as that just described, is used is made clear by Figures 5 and 6 of the drawing. The sheet metal element or structure ID is there shown disposed upon another structure I9, to which it is to be secured by means of a screw 20, having a head 2i provided with a screw driver slot 22 or any other means for turning the screw. The thread 23 of the shank of the screw is made of sufficient width so that when the shank of the screw is passed through an opening 24 in structure l9 and turned to the opening l2 in the sheet metal element or structure ill, the thread will substantially overlap the top of the conical protuberance. Preferably, the pitch of the screw 23 substantially exceeds the thickness of the metal of the element or structure I!) so that the edge of the opening I2 therein which forms the thread may freely enter between adjacent convolutions of the thread as clearly shown in the drawing.

When a protuberance having an unperforated or unweakened offset wall web is used, the screw is relied upon to itself out the small notch corresponding to the cross section of the thread in the substantially vertically extending edge of said offset web. The shallow notch formed by threading the screw through the edge of the offset web is designated by 25 in Figure 5. Of course, if said edge is weakened or ruptured during the operation of forming the protuberance having an offset web, less force is required in threading the screw through the protuberance, the thread of the screw being then relied upon merely to enlarge or shape the weakened portion of said offset web as the screw is threaded through the protuberance.

The position of the screw after the head 2! thereof contacts with the outer surface of the structure is is illustrated in Figure 5. In this position the screw could be readily removed from engagement with the element or structure It by a reverse rotation thereof, no substantial locking action being then present. In order to produce a firm locking engagement between the element l0 and the shank of the screw 20, the screw is turned through approximately one further revolution. Said further rotation of the screw exerts a substantial pressure against the top of the protuberance causing a substantial flattening thereof as illustrated in Figure 6. As the protuberance is flattened, the opening [2 is constricted in size resulting in a firm frictional engagement between the wall of said opening and the shank of the screw at the base of the thread. Inasmuch as the protuberance is unweakened by any radial slit extending from the opening in the top thereof, the size of the opening is reduced uniformly, the protuberance being of substanabove described. The

. cific forms without essential characteristics thereof.

' mit the passage of the t'ially the same strength at every point radially outwardly of the screw. An unusually eflective self-locking action is thus provided between the protuberance and the screw preventing reverse rotation of the screw when this invention is utilized in connection with structures subject to ,vibration.

It is to be understood that in the final position of the screw, anefiective seal is provided between the screw and the opening in the flattened protuberance, because of the uniform engagement of the wall of the opening with the shank of the screw at the base of the thread and because the onset is out only to the thread through the edge thereof.

Figures 7 and 8 illustrate the application of the invention of Figures metal nut 26. The body of said nut is provided with a generally conical protuberance Tl having an opening 28 in the top thereof, and a radially extending offset wall or web 29, corresponding to the generally conical protuberance already well of the opening is shaped to provide a single helical thread. A multiplicity of periphery of the nut 26 and one or both of the edges provided by said slits are bent downwardly providing teeth. While nut 26 is shown circular in form it will be understood that it may be made rectangular, hexagonal or in any other desired shape.

In the use of such a nut as illustrated in Figures 7 and 8, the shank of the bolt is threaded through the opening 2' therein in the manner already described, and rotation of the bolt is continued until it causes a substantial flattening of the protuberance. In flattening said protuberance a substantial'pressure is applied causing the teeth'3l to bite into the structure against which the nut abuts, preventing rotation of the nut with respect to said structure. 'A locking action between the nut and the bolt is also caused by the flattening of the protuberance in the manner already described, so that relative rotation between the bolt and the nut, and between the nut and the structure against which it abuts are this way a self-locking nut, not

prevented. In

the bolt, is

likely tobecome disengaged from provided.

The invention may be embodied in other spedeparting from the spirit or The present embodiment is therefor to be considered in all extent necessary to perbeing shaped to cause 1 to 6, inclusive, to a sheet slits 3|! extend inwardly of the respects as' illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes .which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

What is claimed and desired to be secured by United States Letters Patent is:

l. A sheet metal. structure designed for selflocking threaded engagement by a screw, comprising a protuberance in the sheet metal having an opening in the top thereof, said protuberance the greater portion of the wall of said opening to present a substantially complete single helical thread forvengagement by said screw and to cause the remainder of said wall to extend sharply away from the plane of the'sheet metal surrounding said protuberance in the form of a radial web, the protuberance merging gradually without perforation in every direction from said wall into said plane.

2. A sheet metal structure designed for selflocking threaded engagement by a screw comprising a protuberance extending substantially above the surface plane of said structure, an opening for the passage of said screw in the top .of said protuberance, the wall of said opening being continuous and providing a single helical thread the high and low points of which are interconnected by a radial web resulting from offsetting the metal of the protuberance.

3. The method of adapting a sheet metal structure for the reception of a screw, which consists in pressing a protuberance in the metal, then forming an opening in the center of the protuberance, then shaping the wall of said opening to form a helical thread, and providing an ofiset web in the metal of the protuberance adjacent said opening between the high and low points of said thread.

4. A sheet metal structure designed for self- 7 

